There are three ways to negotiate the price.

First, if you haven't yet started a transaction, you can negotiate from the Listing Details page. You will see a button labeled "Make an Offer." Clicking on that opens up a drawer where you can put in an offer.

If you are in a transaction already, you can do it in the following ways.

From My Feed, click the transaction that you want to negotiate. Look for the label - CURRENT PRICE. Clicking the price opens a drawer where you can adjust the current price.

The other way to negotiate the price is by clicking on "Buyer accepted sale price" or if the seller the "Seller accepted sale price."

This will open a drawer to the right where you can adjust your offer.